Cant apply Glass shader properly?
change your material in this way

result (if you decrease alpha to 0.6):

UPDATE:
i am sorry, i didn't get that you wanted that drag and drop functionality.
I just tried again - and it worked. You can check my video here:
https://youtu.be/U2dKeZhib60
but...please be a little bit patient, because my internet upload is blazingly fa....slow :(
Can you show us a movie/gif so we can see what you are doing (wrong)?